Borg vs Borg = The coolest match ever
Davydenko vs Davydenko = None of them would win.
Safin/Safin vs Safin/Safin = After the match there would only be one left standing.
Gilbert vs Gilbert = Chess where no one would move.
Chang vs Chang = The fastest match ever.
Krajicek/Krajicek vs Krajicek/Krajicek = This might actually be a longer match than Nadal vs Nadal.